Methods for a Gate Replacement Process

ABSTRACT

A method for fabricating a semiconductor device is disclosed. In one embodiment, the method may include providing a substrate; forming a gate structure including a first dummy gate over the substrate; removing the first dummy gate from the gate structure to form a trench; forming an interfacial layer, high-k dielectric layer, and capping layer to partially fill in the trench; forming a second dummy gate over the capping layer, wherein the second dummy gate fills the trench; and replacing the second dummy gate with a metal gate. In one embodiment, the method may include providing a substrate; forming an interfacial layer over the substrate; forming a high-k dielectric layer over the interfacial layer; forming an etch stop layer over the high-k dielectric layer; forming a capping layer including a low thermal budget silicon over the etch stop layer; forming a dummy gate layer over the capping layer; forming a gate structure; and performing a gate replacement process.

PRIORITY DATA

The present application is a divisional application of U.S. patentapplication Ser. No. 12/575,280, filed Oct. 7, 2009, which isincorporated herein by reference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. In the course of IC evolution, functional density (i.e., thenumber of interconnected devices per chip area) has generally increasedwhile geometry size (i.e., the smallest component (or line) that can becreated using a fabrication process) has decreased. This scaling downprocess generally provides benefits by increasing production efficiencyand lowering associated costs. Such scaling down has also increased thecomplexity of processing and manufacturing ICs and, for these advancesto be realized, similar developments in IC processing and manufacturingare needed.

For example, the continuing decrease in technology nodes has led to adesire to replace a conventional polysilicon gate electrode with a metalgate electrode to improve device performance. One process for forming ametal gate structure (e.g., having a metal gate electrode) is referredto as a “gate last” process, where the final gate stack is fabricatedlast. This reduces the number of subsequent processes, including hightemperature processing, that must be performed after formation of thegate structures. However, there are challenges to implementing suchfeatures and processes in conventional fabrication. As the gate lengthand spacing between devices decreases, these problems are exacerbated.For example, gate replacement processes suffer from gap fill issues andneed ways to reduce an equivalent oxide thickness.

Accordingly, what is needed is a method for fabricating an IC devicethat addresses the above stated issues.

SUMMARY

A method for fabricating a semiconductor device is provided. In oneembodiment, the method includes providing a substrate and forming a gatestructure including a first dummy gate over the substrate. The firstdummy gate is removed from the gate structure to form a trench, and aninterfacial layer, high-k dielectric layer, and capping layer is formedto partially fill in the trench. A second dummy gate may be formed overthe capping layer, wherein the second dummy gate fills the trench. Thesecond dummy gate may be replaced with a metal gate. It is understoodthat a gate structure is not limited to a single gate structure and caninclude a plurality of gate structures.

In one embodiment, the method for fabricating a semiconductor deviceincludes providing a substrate; forming an interfacial layer over thesubstrate; forming a high-k dielectric layer over the interfacial layer;forming an etch stop layer over the high-k dielectric layer; forming acapping layer including a low thermal budget silicon over the etch stoplayer; forming a dummy gate layer over the capping layer; forming a gatestructure; and performing a gate replacement process. The gatereplacement process may include replacing at least the dummy gate layerand capping layer including the low thermal budget silicon with a metalgate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of a method for fabricating an integrated circuitdevice according to aspects of the present disclosure; and

FIGS. 2A-2N are various cross-sectional views of embodiments of anintegrated circuit device during various fabrication stages according tothe method of FIG. 1.

FIG. 3 is a flow chart of a method for fabricating an integrated circuitdevice according to aspects of the present disclosure; and

FIGS. 4A-4G are various cross-sectional views of embodiments of anintegrated circuit device during various fabrication stages according tothe method of FIG. 3.

DETAILED DESCRIPTION

The present disclosure relates generally to methods for manufacturingintegrated circuit devices, and more particularly, to gate replacementprocesses (or methods).

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of theinvention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

With reference to FIGS. 1, 2A-2N, 3, and 4A-4E, methods 100, 300 andsemiconductor devices 200, 400 are collectively described below. Thesemiconductor devices 200, 400 illustrate an integrated circuit, orportion thereof, that can comprise memory cells and/or logic circuits.The semiconductor devices 200, 400 can include passive components suchas resistors, capacitors, inductors, and/or fuses; and activecomponents, such as P-channel field effect transistors (PFETs),N-channel field effect transistors (NFETs), metal-oxide-semiconductorfield effect transistors (MOSFETs), complementarymetal-oxide-semiconductor transistors (CMOS s), high voltagetransistors, and/or high frequency transistors; other suitablecomponents; and/or combinations thereof. It is understood thatadditional steps can be provided before, during, and after the methods100, 300, and some of the steps described below can be replaced oreliminated, for additional embodiments of the methods. It is furtherunderstood that additional features can be added in the semiconductordevices 200, 400, and some of the features described below can bereplaced or eliminated, for additional embodiments of the semiconductordevices 200, 400.

In the present embodiments, the semiconductor devices 200, 400 arefabricated in a gate last process. Alternatively, the semiconductordevices 200, 400 may be fabricated in a gate first process or hybridprocess including a gate first process and a gate last process. In thegate last process, a dummy poly gate structure is formed first and thenthe dummy poly gate structure may be removed and replaced with a metalgate structure. In the gate first process, a metal gate structure may beformed first and may be followed by a CMOS process flow to fabricate thefinal device. In the hybrid gate process, a metal gate structure of onetype of device may be formed first and a metal gate structure of anothertype of device may be formed last. Further, in some embodiments, thegate last process, gate first process, or hybrid process may form a gatestructure comprising polysilicon.

Double Dummy Gate Deposition Method

FIG. 1 is a flow chart of one embodiment of the method 100 forfabricating the semiconductor device 200 in a “gate last” process. FIGS.2A-2N are various cross-sectional views of the semiconductor device 200according to one embodiment, in portion or entirety, during variousfabrication stages of the method 100. Conventional gate replacementprocesses utilize a single dummy gate patterning approach. As technologynodes continue to decrease, particularly to 22 nm technology nodes andbelow, a gate length (L_(g)) continues to decrease and become smaller.It has been observed that the single dummy gate patterning approach maysuffer from gap fill issues as gate lengths (or gate trenches) becomesmaller. The single dummy gate patterning approach also involvesseparate removal approaches for forming more than one device, such as ap-type device and an n-type device. This often requires two high-kdielectric layer deposition processes, which may present undesirableissues. Accordingly, the method 100 implements a double dummy gatedeposition method. The double dummy gate deposition method can prevent(or eliminate) gap fill issues arising from small gate trenches (orlengths), and can provide a single high-k dielectric layer depositionprocess, which prevents issues arising from the current high-kdielectric layer double deposition process. It is understood thatdifferent embodiments may have different advantages, and that noparticular advantage is necessarily required of any embodiment.

Referring to FIGS. 1 and 2A, the method 100 begins at block 102 where asubstrate 210 including a first region 211A and a second region 211B isprovided. In the present embodiment, the substrate 210 is asemiconductor substrate comprising silicon. Alternatively, the substrate210 comprises an elementary semiconductor including silicon and/orgermanium in crystal; a compound semiconductor including siliconcarbide, gallium arsenic, gallium phosphide, indium phosphide, indiumarsenide, and/or indium antimonide; an alloy semiconductor includingSiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. The alloy semiconductor substrate may have agradient SiGe feature in which the Si and Ge composition change from oneratio at one location to another ratio at another location of thegradient SiGe feature. The alloy SiGe may be formed over a siliconsubstrate. The SiGe substrate may be strained. Furthermore, thesemiconductor substrate may be a semiconductor on insulator (SOI). Insome examples, the semiconductor substrate may include a doped epilayer. In other examples, the silicon substrate may include a multilayercompound semiconductor structure.

The substrate 210 may include various doped regions depending on designrequirements as known in the art (e.g., p-type wells or n-type wells).The doped regions are doped with p-type dopants, such as boron or BF₂;n-type dopants, such as phosphorus or arsenic; or combinations thereof.The doped regions may be formed directly on the substrate 210, in aP-well structure, in a N-well structure, in a dual-well structure, orusing a raised structure. The semiconductor substrate 210 may furtherinclude various active regions, such as regions configured for an N-typemetal-oxide-semiconductor transistor device (referred to as an NMOS) andregions configured for a P-type metal-oxide-semiconductor transistordevice (referred to as a PMOS). In the present embodiment, the substrate210 includes first region 211A configured for a PMOS device and secondregion 211B configured for a NMOS device. It is understood that thesemiconductor device 200 may be formed by CMOS technology processing,and thus some processes are not described in detail herein.

One exemplary isolation region 212 is formed on the substrate 210 toisolate various regions (e.g., first and second regions 211A, 211B) ofthe substrate 210, and in the present embodiment, to isolate the NMOSand PMOS device regions. The isolation region 212 utilizes isolationtechnology, such as local oxidation of silicon (LOCOS) or shallow trenchisolation (STI), to define and electrically isolate the various firstand second regions 211A, 211B. In the present embodiment, the isolationregion 212 includes a STI. The isolation region 212 comprises siliconoxide, silicon nitride, silicon oxynitride, other suitable materials, orcombinations thereof. The isolation region 212 is be formed by anysuitable process. As one example, the formation of an STI includes aphotolithography process, etching a trench in the substrate (forexample, by using a dry etching and/or wet etching), and filling thetrench (for example, by using a chemical vapor deposition process) withone or more dielectric materials. In some examples, the filled trenchmay have a multi-layer structure such as a thermal oxide liner layerfilled with silicon nitride or silicon oxide.

One or more gate structures are formed over the substrate 210—at leastone gate structure is formed over the substrate in the first region 211Aand at least one gate structure is formed over the substrate in thesecond region 211B. In the present embodiment, a first gate structure220 is formed within the first/PMOS region 211A, and a second gatestructure 230 is formed within the second/NMOS region 211B. It isunderstood that a plurality of gate structures may be formed over thesubstrate 210 in the first and second regions 211A, 211B. The gatestructures 220, 230 are formed by any suitable process. For example, thegate structures are formed by a procedure including deposition,photolithography patterning, and etching processes. The depositionprocesses include chemical vapor deposition (CVD), physical vapordeposition (PVD), atomic layer deposition (ALD), high density plasma CVD(HDPCVD), metal organic CVD (MOCVD), remote plasma CVD (RPCVD), plasmaenhanced CVD (PECVD), plating, other suitable methods, and/orcombinations thereof. The photolithography patterning processes includephotoresist coating (e.g., spin-on coating), soft baking, mask aligning,exposure, post-exposure baking, developing the photoresist, rinsing,drying (e.g., hard baking), other suitable processes, and/orcombinations thereof. Alternatively, the photolithography exposingprocess is implemented or replaced by other proper methods such asmaskless photolithography, electron-beam writing, and ion-beam writing.The etching processes include dry etching, wet etching, and/or otheretching methods (e.g., reactive ion etching). The etching processes alsoinclude either purely chemical (wet etching), purely physical (ionmilling), and/or combinations thereof. It is understood that the gatestructures may be formed simultaneously, utilizing the same processingsteps and processing materials; independently of one another, utilizingvarying processing steps and processing materials; or using acombination of simultaneous and independent processing steps andprocessing materials.

In the present embodiment, the gate structures 220, 230 comprise gatestacks having the interfacial layer 222, 232 and first dummy gate layer224, 234. The gate stack is formed by any suitable process, includingthe processes described herein. In one example, an interfacial layer anda first dummy gate layer are deposited over the substrate 210. Then, alayer of photoresist is formed over the first dummy gate layer by asuitable process, such as spin-on coating, and patterned to form apatterned photoresist feature. The pattern of the photoresist can thenbe transferred by a dry etching process to the underlying layers (i.e.,the interfacial layer and first dummy gate layer) to form the gatestacks comprising interfacial layer 222, 232 and dummy gate layer 224,234 as shown in FIG. 2A. The photoresist layer may be strippedthereafter. In another example, a hard mask layer is formed over thefirst dummy gate layer; a patterned photoresist layer is formed on thehard mask layer; the pattern of the photoresist layer is transferred tothe hard mask layer and then transferred to the first dummy gate layerand the interfacial layer to form the gate stack of the gate structures220, 230. It is understood that the above examples do not limit theprocessing steps that may be utilized to form the gate stack. It isfurther understood that the gate stack of the gate structures 220, 230may comprise additional layers. For example, the gate structures 220,230 may comprise interfacial layers, capping layers, diffusion/barrierlayers, conductive layers, other suitable layers, and/or combinationsthereof. Also, the semiconductor device 200 may include one or moreantireflective coating layers (e.g., a top antireflective coating layerand/or a bottom antireflective coating layer).

The interfacial layer 222, 232 is formed over the substrate 210. Theinterfacial layer 222, 232 is formed by any suitable process to anysuitable thickness. For example, the interfacial dielectric layer 222,232 includes a silicon oxide layer (e.g., thermal oxide or chemicaloxide) having a thickness ranging from about 10 angstroms (Å) to about35 Å. Alternatively, the interfacial layer 222, 232 comprises siliconoxynitride (SiON). In an example, before the interfacial dielectriclayer 222, 232 is grown over the substrate 210, a last pre-gate clean(e.g., utilizing an HF solution) and UV process may be performed.

The first dummy gate layer 224, 234 is formed over the interfacial layer222, 232 by any suitable process to any suitable thickness. The firstdummy gate layer 224, 234 may comprise multiple material layers. In thepresent example, the first dummy gate layer 224, 234 comprisespolysilicon. The semiconductor device 200 may further include a hardmask layer (not shown) formed over the first dummy gate layer 224, 234.The hard mask layer may include silicon nitride, silicon oxynitride,silicon carbide, and/or other suitable dielectric materials, and may beformed using any suitable method, such as CVD, PVD, or sputtering.

A sealing layer 226, 236 may be formed on the sidewalls of the gatestacks of the gate structures 220, 230. In the present embodiment, thesealing layer 226, 236 is formed on the sidewalls of the interfaciallayer 222, 232 and first dummy gate layer 224, 234. The sealing layer226, 236 includes a dielectric material, such as silicon nitride,silicon oxynitride, silicon carbide, other suitable material, and/orcombinations thereof. The sealing layer 226, 236 may include a singlelayer or multiple layer configuration. It should be noted that thesealing layer 226, 236 may protect the gate stacks of the gatestructures 220, 230 from damage or loss during subsequent processing,and may also prevent oxidation during subsequent processing. The sealinglayer 226, 236 is formed by any suitable process to any suitablethickness.

Spacers may further be formed on the sidewalls of the gate stacks. Forexample, spacer liner 227, 237 and gate spacers 228, 238 may be formed.The spacer liner 227, 237 and gate spacers 228, 238 are formed by anysuitable process to any suitable thickness. The spacer liner 227, 228may comprise an oxide material (e.g., silicon oxide), and the gatespacers 228, 238, which are positioned on each side of the gatestructures 220, 230, may comprise a nitride material (e.g., siliconnitride). In various examples, the gate spacers 228, 238 comprise adielectric material such as silicon nitride, silicon carbide, siliconoxynitride, other suitable materials, and/or combinations thereof. Thegate spacers 228, 238 may be used to offset subsequently formed dopedregions, such as heavily doped source/drain regions.

Various doped regions may also be formed in the substrate 210. Forexample, various doped regions comprise lightly doped source/drain (LDD)regions 242, 243 and source/drain (S/D) regions 244, 245 (also referredto as heavily doped S/D regions). The LDD regions 242, 243 and S/Dregions 244, 245 are formed by one or more ion implantation processes,photolithography, diffusion, and/or other suitable processes. The dopingspecies may depend on the type of device being fabricated, such as anNMOS or PMOS device. For example, the LDD regions 242, 243 and S/Dregions 244, 245 are doped with p-type dopants, such as boron or BF₂;n-type dopants, such as phosphorus or arsenic; and/or combinationsthereof. The LDD regions 242, 243 and S/D regions 244, 245 may comprisevarious doping profiles. It is understood that the LDD regions may beformed prior to formation of the gate spacers 228, 238, and the LDDregions may be aligned with an outer edge of the sealing layers 226, 236following one or more implantation processes. Additionally, one or moreannealing processes may be performed to activate the LDD regions 242,243 and/or S/D regions 244, 245. The annealing processes comprise rapidthermal annealing (RTA) and/or laser annealing processes. It should benoted that during a subsequent annealing process (e.g., activationprocess) the dopants in the LDD regions 242, 243 may diffuse towards thesidewalls of the gate stack comprising the high-k dielectric layer 222,232 and dummy gate layer 224, 234 such that a portion of each of the LDDregions 242, 243 may extend underneath a portion of the sealing layer226, 236. The S/D regions 244, 245 may be aligned with an outer edge ofthe spacers 228, 238 following the one or more implantation processes.

The doped regions may be formed directly in the semiconductor substrate,in a P-well structure, in a N-well structure, in a dual-well structure,or using a raised structure. In some examples, the S/D regions 244, 245include raised S/D regions, which may be formed by one or more epitaxyprocesses, such that SiGe features can be formed in a crystalline statein the substrate 210. The epitaxy processes include CVD depositiontechniques (e.g., vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD(UHV-CVD)), molecular beam epitaxy, and/or other suitable processes. Theepitaxy process may use gaseous and/or liquid precursors, which interactwith the composition of the substrate 210 (e.g., silicon). Thus, astrained channel may be achieved in the first or second regions 211A,211B, depending on device configuration, to increase carrier mobilityand enhance device performance.

One or more contact features 248, 249, such as silicide regions, mayalso be formed. The contact features 248, 249 are coupled to the S/Dregions 244, 245. The contact features 248, 249 comprise silicidematerials such as nickel silicide (NiSi), nickel-platinum silicide(NiPtSi), nickel-platinum-germanium silicide (NiPtGeSi),nickel-germanium silicide (NiGeSi), ytterbium silicide (YbSi), platinumsilicide (PtSi), iridium silicide (IrSi), erbium silicide (ErSi), cobaltsilicide (CoSi), other suitable materials, and/or combinations thereof.The contact features 248, 249 are formed by any suitable process,including the processes described herein. In the present embodiment, thecontact features 248, 249 may be formed by a salicide (self-alignedsilicide) process. For example, a metal material may be deposited overthe substrate, including over the substrate (e.g., silicon regions)and/or doped regions. After deposition, the salicidation process maycontinue with a reaction between the deposited metal material and thesilicon regions at an elevated temperature that is selected based on thespecific metal material or materials. This is also referred to asannealing, which may be a RTP. The unreacted metal material is removedthereafter. The reacted silicide may require additional thermal processto reduce the resistance of the silicide.

A dielectric layer 250 is disposed over the substrate 210, such as aninterlayer (or inter-level) dielectric (ILD) layer. The dielectric layer250 comprises any suitable dielectric material including TEOS oxide,silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide,zirconium oxide, titanium oxide, aluminum oxide, hafnium dioxide-alumina(HfO₂—Al₂O₃) alloy, PSG, BPSG, other suitable dielectric materials,and/or combinations thereof. Alternatively, the dielectric layer 250comprises a low-k dielectric material, such as fluorinated silica glass(FSG), carbon doped silicon oxide, Black Diamond® (Applied Materials ofSanta Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon,Parylene, BCB (bis-benzocyclobutenes), SiLK (Dow Chemical, Midland,Mich.), polyimide, other proper materials, and/or combinations thereof.The dielectric layer 250 is formed by any suitable process to anysuitable thickness, including by CVD, high density plasma CVD, spin-on,sputtering, and/or other suitable methods. The dielectric layer 250 mayfurther include a multilayer structure comprising multiple dielectricmaterials. It is understood that additional layers may be formedoverlying and/or underlying the dielectric layer 250.

Referring to FIGS. 1 and 2B, at block 104, the first dummy gate layer isremoved from the gate structures in the first and second regions,thereby forming openings in the gate structures. For example, the firstdummy gate layer 224, 234 is removed from gate structures 220, 230 byany suitable process. As also illustrated, the interfacial layer 222,232 may also be removed, simultaneously with or independent of the firstdummy gate layer 224, 234. Removing dummy gate layer 224, 234 (andinterfacial layer 222, 232) may include one or more etching processes,including wet etching processes, dry etching processes, or combinationsthereof. The removed interfacial layer 222, 232 and first dummy gatelayer 224, 234 form an opening (or trench) in the gate structures 220,230.

At block 106, as illustrated in FIGS. 2C and 2D, a high-k dielectriclayer 252 and a capping layer 254 are formed over the substrate 210and/or over the openings of the gate structures 220, 230. Particularly,the high-k dielectric layer 252 and capping layer 254 partially fill theopenings of the gate structures 220, 230 in the first and second regions211A, 211B. An interfacial layer may be formed between the semiconductorsubstrate 210 and the high-k dielectric material layer 252. For example,an interfacial layer including a thin silicon oxide layer can be formedon the substrate 210 before forming the high-k dielectric material layer252 to a thickness ranging from about 5 Å to about 10 Å. The thinsilicon oxide layer is formed by an ALD or thermal oxidation process. Itis understood that the interfacial layer may be similar to interfaciallayer 222, 232 described above.

The high-k dielectric layer 252 is formed by any suitable process to anysuitable thickness. For example, the high-k dielectric layer 252 isformed by an ALD process to a thickness ranging from about 10 Å to about30 Å. The high-k dielectric layer 252 comprises a high-k dielectricmaterial, such as HfO₂, HfSiO, HfSiON, HfTaO, HfSiO, HfZrO, othersuitable high-k dielectric materials, and/or combinations thereof. Asnoted above, the method 100 provides for a single high-k dielectriclayer formation process. This may improve or eliminate issues arisingfrom the double high-k dielectric deposition processes utilized inconventional processing.

The capping layer 254 is formed by any suitable process to any suitablethickness. For example, the capping layer 254 is formed by an ALD or PVDprocess to a thickness ranging from about 20 Å to about 40 Å. Thecapping layer 254 comprises titanium, titanium nitride, tantalum,tantalum nitride, other suitable materials, and/or combinations thereof.In the present example, the capping layer 254 comprises titanium nitride(TiN).

At block 108, referring to FIGS. 2E and 2F, a second dummy gate layer isformed over the substrate by any suitable process to any suitablethickness. For example, second dummy gate layer 256 is formed over thesubstrate 210 (and capping layer 254) to fill the remainder of theopenings (trenches) in the gate structures 220, 230. In the presentexample, the second dummy gate layer 256 comprises polysilicon depositedby a CVD or PVD process. The second dummy gate layer 256 is deposited ata lower temperature than the first dummy gate layer 224, 234. The seconddummy gate layer 256 may comprise multiple material layers. The seconddummy gate layer 256 may be similar to the first dummy gate layer 224,234. Subsequent to the deposition of the second dummy gate layer 256,one or more chemical mechanical polishing (CMP) processes may beperformed, for example, until the capping layer 254 is reached asillustrated in FIG. 2F. It is understood that the second dummy gatelayer 256 may comprise other suitable materials.

Referring to FIGS. 2G-2O, at blocks 110, 112, 114, 116, 118, and 120, agate replacement process is performed. More particularly, a metal gatemay replace the dummy poly gate of gate structures 220, 230 (i.e., agate layer replaces the dummy gate layer 256). The metal gate maycomprise one or more layers and/or materials. A patterned layer may beformed by conventional photolithography and patterning processes tooverlay (or protect) a region of the substrate, wherein a gate of afirst work function is formed in the gate structures of one region(e.g., first region 211A) while protecting another region (e.g., secondregion 211B), and vice versa. With reference to FIGS. 2G-2K, and atblocks 110, 112, 114, a gate structure having a first work function isformed. With reference to FIGS. 2L-2O, and at blocks 116, 118, 120, agate structure having a second work function is formed.

At block 110, the second dummy gate layer is removed from the gatestructure in the first region, thereby forming a first opening (trench).Referring to FIGS. 2G and 2H, the second dummy gate layer 256 is removedfrom the gate structure 220 in the first/PMOS region 211A to form afirst opening (trench). For example, a patterned layer (including a hardmask layer 258 and a photoresist layer 260) is formed over the gatestructure 230 of the second/NMOS region 211B to protect the gatestructure 230 from subsequent processing. The patterned layer is formedby conventional photolithography and patterning processes, such as thoseprocesses described herein. The hard mask layer 258 includes anysuitable material, such as silicon nitride, SiON, SiC, SiOC, spin-onglass (SOG), a low-k film, tetraethylorthosilicate (TEOS), plasmaenhanced CVD oxide (PE-oxide), high-aspect-ratio-process (HARP) formedoxide, or other suitable material. The hard mask layer 258 includes anysuitable thickness. In an example, the hard mask layer 258 includes aPE-oxide or titanium nitride (TiN) layer having a thickness ranging fromabout 40 Å to about 100 Å. The photoresist layer 260 comprises anysuitable material and includes a positive-type or negative-type resistmaterial. An exemplary photoresist layer 260 includes a chemicalamplifying (CA) resist layer.

The second dummy gate layer 256 is then removed from the gate structure220 in the first/PMOS region 211A by any suitable process to form thefirst opening (trench). The first opening (trench) may be formed by oneor more dry etching processes, wet etching processes, and/orcombinations thereof. The etching process may include multiple etchingsteps to etch various material layers. For example, the dry etchingprocess may use a fluorine-containing plasma (e.g., etch gas includesCF₄). In another example, the second dummy gate layer 256 is selectivelyetched away. Subsequently, the patterned layer may be removed by astripping or ashing process or etching process. It is understood thatthe patterned hard mask layer 258 and photoresist layer 260 may beremoved simultaneously or independently from the second dummy gate layer256, using the same of different processes.

At blocks 112 and 114, a metal gate is formed in the first region. Themetal gate may comprise a work function material and an additionalconductive layer. Referring to FIG. 21, at block 112, a first gate layer262 is formed over the substrate 210 to partially fill in the firstopening (trench) by any suitable process to any suitable thickness. Thefirst gate layer 262 may comprise a work function layer. The workfunction layer includes any suitable material, such as aluminum, copper,tungsten, titanium, tantulum, titanium nitride, tantalum nitride, nickelsilicide, cobalt silicide, silver, TaC, TaSiN, TaCN, TiAl, TiAlN, WN,metal alloys, other suitable materials, and/or combinations thereof.Exemplary work function layers for an NMOS device include tantalumnitride, titanium aluminum, titanium aluminum nitride, or combinationsthereof; and exemplary work function layers for a PMOS device mayinclude tungsten, titanium nitride, tungsten nitride, or combinationsthereof. In the present example, the first gate layer 262 includes ap-type work function material (e.g., TiN, W, or WN) formed by an ALD orPVD process to a thickness ranging from about 20 Å to about 150 Å.

At block 114, a first conductive layer 264 is then formed over the firstgate layer 262 to substantially fill in the remainder of the firstopening as illustrated in FIG. 2J. The first conductive layer 264includes any suitable material, such as aluminum, copper, tungsten,titanium, tantulum, titanium nitride, tantalum nitride, nickel silicide,cobalt silicide, silver, TaC, TaSiN, TaCN, TiAl, TiAlN, WN, metalalloys, other suitable materials, and/or combinations thereof. In thepresent example, the first conductive layer 264 comprises aluminum. Thefirst conductive layer 264 is formed by any suitable process to anysuitable thickness, such as an ALD or a PVD process. Subsequently, oneor more CMP processes may be performed to planarize the first conductivelayer 264. As illustrated in FIG. 2K, the CMP process may be performeduntil the capping layer 254 is reached, forming a metal gate having afirst work function in the gate structure 220.

At block 116, the second dummy gate layer is removed from the gatestructure in the second region, thereby forming a second opening(trench). Referring to FIGS. 2L and 2M, the second dummy gate layer 256is removed from the gate structure 230 in the second/NMOS region 211B toform a second opening (trench). For example, a patterned layer(including a hard mask layer 266 and a photoresist layer 268) is formedover the gate structure 220 of the first/PMOS region 211A to protect thegate structure 220 from subsequent processing. The patterned layer isformed by conventional photolithography and patterning processes, suchas those processes described herein. The hard mask layer 266 includesany suitable material, such as silicon nitride, SiON, SiC, SiOC, spin-onglass (SOG), a low-k film, tetraethylorthosilicate (TEOS), plasmaenhanced CVD oxide (PE-oxide), high-aspect-ratio-process (HARP) formedoxide, or other suitable material. The hard mask layer 266 includes anysuitable thickness. In an example, the hard mask layer 266 includes aPE-oxide or titanium nitride (TiN) layer having a thickness ranging fromabout 40 Å to about 100 Å. The photoresist layer 268 comprises anysuitable material and includes a positive-type or negative-type resistmaterial. An exemplary photoresist layer 268 includes a chemicalamplifying (CA) resist layer.

The second dummy gate layer 256 is then removed from the gate structure230 in the second/NMOS region 211B by any suitable process to form thesecond opening (trench). The second opening (trench) may be formed byone or more dry etching processes, wet etching processes, and/orcombinations thereof. The etching process may include multiple etchingsteps to etch various material layers. For example, the dry etchingprocess may use a fluorine-containing plasma (e.g., etch gas includesCF₄). In another example, the second dummy gate layer 256 is selectivelyetched away. Subsequently, the patterned layer may be removed by astripping or ashing process or etching process. It is understood thatthe patterned hard mask layer 266 and photoresist layer 268 may beremoved simultaneously or independently from the second dummy gate layer256, using the same of different processes.

Referring to FIG. 2N, at blocks 118 and 120, a metal gate is formed inthe second region. The metal gate may comprise a work function materialand a conductive layer. At block 118, a second gate layer 270 is formedover the substrate 210 to partially fill in the second opening (trench)by any suitable process to any suitable thickness. The second gate layer270 may comprise a work function layer. The work function layer includesany suitable material, such as aluminum, copper, tungsten, titanium,tantulum, titanium nitride, tantalum nitride, nickel silicide, cobaltsilicide, silver, TaC, TaSiN, TaCN, TiAl, TiAlN, WN, metal alloys, othersuitable materials, and/or combinations thereof. Exemplary work functionlayers for an NMOS device include tantalum nitride, titanium aluminum,titanium aluminum nitride, or combinations thereof; and exemplary workfunction layers for a PMOS device may include tungsten, titaniumnitride, tungsten nitride, or combinations thereof. In the presentexample, the second gate layer 270 includes a n-type work functionmaterial (e.g., TiAl or TiAlN) formed by an ALD or PVD process to athickness ranging from about 20 Å to about 150 Å.

At block 120, a second conductive layer 272 is then formed over thesecond gate layer 270 to substantially fill in the remainder of thesecond opening as illustrated in FIG. 2N. The second conductive layer272 includes any suitable material, such as aluminum, copper, tungsten,titanium, tantulum, titanium nitride, tantalum nitride, nickel silicide,cobalt silicide, silver, TaC, TaSiN, TaCN, TiAl, TiAlN, WN, metalalloys, other suitable materials, and/or combinations thereof. In thepresent example, the second conductive layer 272 comprises aluminum. Thesecond conductive layer 272 is formed by any suitable process to anysuitable thickness, such as an ALD or a PVD process. Subsequently, oneor more CMP processes may be performed to planarize the secondconductive layer 272. The CMP process may further planarize thesemiconductor device 200.

It is understood that the n-metal and p-metal structures may be formedin any order. Further, during the formation of the metal gate structuresfor the first/PMOS device region 211A and the second/NMOS device region211B, N/P patterning may be implemented to separate one type of devicefrom the other, and vice versa. The metal gates may further compriseliner layers, work function layers, fill layers, other suitable layers,and/or combinations thereof. It is also understood that thesemiconductor device 200 may undergo further CMOS or MOS technologyprocessing to form various features known in the art. Subsequentprocessing may form various contacts/vias/lines and multilayerinterconnect features (e.g., metal layers and interlayer dielectrics) onthe substrate 210, configured to connect the various features orstructures of the semiconductor device 200. The additional features mayprovide electrical interconnection to the device including the formedmetal gate structures. For example, a multilayer interconnectionincludes vertical interconnects, such as conventional vias or contacts,and horizontal interconnects, such as metal lines. The variousinterconnection features may implement various conductive materialsincluding copper, tungsten, and/or silicide. In one example a damasceneand/or dual damascene process is used to form a copper relatedmultilayer interconnection structure.

In summary, a gate replacement process is provided. The gate replacementprocess described implements a double dummy gate deposition process,which addresses issues found in conventional processing (e.g.,preventing gap fill issues as gate lengths become smaller and providinga single high-k dielectric layer deposition process). A first dummy gateand a second dummy gate may be provided to fabricate the semiconductordevice 200. In an example, the method comprises removing a first dummygate to form a first trench; forming a high-k dielectric layer, acapping layer, and/or a second dummy gate within the first trench;removing the second dummy gate to form a second trench in a firstregion; forming a first gate within the second trench; removing thesecond dummy gate to form a third trench in a second region; and forminga second gate within the third trench. The resulting semiconductordevice may comprise a plurality of NMOS and PMOS devices.

Low Thermal Budget Silicon Capping Layer Method

FIG. 3 is a flow chart of one embodiment of the method 300 forfabricating the semiconductor device 400 in a “gate last” process. FIGS.4A-4G are various cross-sectional views of the semiconductor device 400according to one embodiment, in portion or entirety, during variousfabrication stages of the method 300. Conventional gate replacementprocesses strive to reduce an equivalent oxide thickness (EOT) exhibitedby an integrated circuit device. In these integrated circuit device, athickness of an interfacial layer is a substantial portion of the EOTexhibited by the final fabricated device, particularly in high-k/metalgate devices. Thus, reducing the thickness of the interfacial layer canimprove EOT scaling.

The initial thickness of the interfacial layer may be easily reduced bya pre-clean process, such as a diluted HF (DHF) dipping process.However, it has been observed that the final thickness of theinterfacial layer depends on a thermal budget, not necessarily theinitial thickness. For example, re-growth of the interfacial layerresults from oxygen transporting from the substrate during high thermalbudget processes (e.g., a source/drain annealing process). Thisdetrimentally affects the EOT of the final device. The method 400introduces an etch stop layer and a low thermal budget silicon cappinglayer over the over the high-k dielectric layer/interfacial layer. Theetch stop layer can minimize the oxygen content absorbed by theinterfacial layer from the substrate during subsequent high thermalbudget processes. The etch stop layer essentially absorbs oxygen fromthe interfacial layer to facilitate EOT reduction. The low thermalbudget silicon capping layer can help control oxygen content in the etchstop layer. Implementing the etch stop layer and low thermal budgetsilicon capping layer barely impacts current replacement gate processflows and can provide significant EOT reduction. It is understood thatdifferent embodiments may have different advantages, and that noparticular advantage is necessarily required of any embodiment.

Referring to FIGS. 1 and 4A, the method 300 begins at block 302 whereina substrate 410 including a first region 411A and a second region 411Bis provided. In the present embodiment, the substrate 410 is asemiconductor substrate comprising silicon. Alternatively, the substrate410 comprises an elementary semiconductor including silicon and/orgermanium in crystal; a compound semiconductor including siliconcarbide, gallium arsenic, gallium phosphide, indium phosphide, indiumarsenide, and/or indium antimonide; an alloy semiconductor includingSiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. The alloy semiconductor substrate may have agradient SiGe feature in which the Si and Ge composition change from oneratio at one location to another ratio at another location of thegradient SiGe feature. The alloy SiGe may be formed over a siliconsubstrate. The SiGe substrate may be strained. Furthermore, thesemiconductor substrate may be a semiconductor on insulator (SOI). Insome examples, the semiconductor substrate may include a doped epilayer. In other examples, the silicon substrate may include a multilayercompound semiconductor structure.

One exemplary isolation region 412 is formed on the substrate 410 toisolate various regions (e.g., first and second regions 411A, 411B) ofthe substrate 410, and in the present embodiment, to isolate the NMOSand PMOS device regions. The isolation region 412 utilizes isolationtechnology, such as local oxidation of silicon (LOCOS) or shallow trenchisolation (STI), to define and electrically isolate the various firstand second regions 411A, 411B. In the present embodiment, the isolationregion 412 includes a STI. The isolation region 412 comprises siliconoxide, silicon nitride, silicon oxynitride, other suitable materials, orcombinations thereof. The isolation region 412 is formed by any suitableprocess. As one example, the formation of an STI includes aphotolithography process, etching a trench in the substrate (forexample, by using a dry etching and/or wet etching), and filling thetrench (for example, by using a chemical vapor deposition process) withone or more dielectric material. In some examples, the filled trench mayhave a multi-layer structure such as a thermal oxide liner layer filledwith silicon nitride or silicon oxide.

The substrate 410 may include various doped regions depending on designrequirements as known in the art (e.g., p-type wells or n-type wells).The doped regions may be doped with p-type dopants, such as boron orBF₂, and/or n-type dopants, such as phosphorus or arsenic. The dopedregions may be formed directly on the substrate 410, in a P-wellstructure, in a N-well structure, in a dual-well structure, or using araised structure. The semiconductor substrate 410 may further includevarious active regions, such as regions configured for an N-typemetal-oxide-semiconductor transistor device (referred to as an NMOS) andregions configured for a P-type metal-oxide-semiconductor transistordevice (referred to as a PMOS). In the present embodiment, the substrate410 includes first region 411A configured for a NMOS device and secondregion 411B configured for a PMOS device. More particularly, the firstregion 411A includes an p-well region 414A, and the second region 411Bincludes a n-well region 414B. It is understood that the semiconductordevice 400 may be formed by CMOS technology processing, and thus someprocesses are not described in detail herein.

At block 304, a material layer is formed over the substrate 410. Thematerial layer includes one or more material layers comprising anysuitable material and thickness. For example, the material layerincludes an interfacial layer 416 and a high-k dielectric layer 418. Thematerial layer is formed by any suitable process including chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), high density plasma CVD (HDPCVD), metal organic CVD(MOCVD), remote plasma CVD (RPCVD), plasma enhanced CVD (PECVD),plating, other suitable methods, and/or combinations thereof.

The interfacial layer 416 and high-k dielectric layer 418 are formedover the substrate 410 by any suitable process to any suitablethickness. For example, the interfacial layer 416 may include a grownsilicon oxide layer (e.g., thermal oxide or chemical oxide).Alternatively, the interfacial layer 416 may comprise silicon oxynitride(SiON). In an example, before the interfacial layer 416 is grown overthe substrate 410, a last pre-gate clean (e.g., utilizing an HFsolution) and UV process may be performed. The high-k dielectric layer418 comprises a high-k dielectric material, such as HfO₂, HfSiO, HfSiON,HfTaO, HfTiO, HfZrO, other suitable high-k dielectric materials, and/orcombinations thereof.

At block 306, an etch stop layer 420 is formed over the substrate 410.The etch stop layer 420 is also formed over the interfacial and high-kdielectric layers 416, 418. The etch stop layer 420 comprises titanium,titanium nitride, tantalum, tantalum nitride, other suitable material,and/or combinations thereof. In the present example, the etch stop layer420 comprises titanium nitride (TiN). As noted above, the etch stoplayer 420 minimizes the oxygen content absorbed by the interfacial layer416 from the substrate during subsequent high thermal budget processes.The etch stop layer 420 absorbs oxygen from the interfacial layer 416 tofacilitate EOT reduction.

As further noted above, it is advantageous to control the oxygen contentof the etch stop layer 420. Thus, in the present embodiment, at block308, a capping layer 422 is formed over the substrate 410. The cappinglayer 422 is also formed over the etch stop layer 420 and material layerincluding interfacial and high-k dielectric layers 416, 418. The cappinglayer 422 comprises a low thermal budget silicon layer, such as asilicon layer deposited by a physical vapor deposition (PVD) process.The capping layer 422 including the low thermal budget silicon controlsthe oxygen content in the etch stop layer 420, which further preventsthe interfacial layer 416 from growing during subsequent processing, andfurther reduces the equivalent oxide thickness.

At block 310, a dummy gate layer 424 is formed over the substrate 410.The dummy gate layer 424 is further formed over the capping layer 422,etch stop layer 418, and material layer including interfacial and high-kdielectric layers 416, 418. The dummy gate layer 424 is formed by anysuitable process to any suitable thickness. The dummy gate layer 424comprises any suitable material. In the present example, the dummy gatelayer 424 comprises a silicon layer formed by a low pressure CVDprocess. The dummy gate layer 424 may comprise multiple material layers.

Referring to FIGS. 3 and 4B-4C, at block 312, a first gate structure anda second gate structure are formed over the substrate 410—at least onegate structure is formed over the substrate in the first region 411A andat least one gate structure is formed over the substrate in the secondregion 411B. In the present embodiment, a first gate structure is formedwithin the first/NMOS region 411A, and a second gate structure is formedwithin the second/PMOS region 411B. The gate structures are formed byany suitable process. For example, the gate structures are formed by aprocedure including deposition, photolithography patterning, and etchingprocesses. The deposition processes include chemical vapor deposition(CVD), physical vapor deposition (PVD), atomic layer deposition (ALD),high density plasma CVD (HDPCVD), metal organic CVD (MOCVD), remoteplasma CVD (RPCVD), plasma enhanced CVD (PECVD), plating, other suitablemethods, and/or combinations thereof. The photolithography patterningprocesses include photoresist coating (e.g., spin-on coating), softbaking, mask aligning, exposure, post-exposure baking, developing thephotoresist, rinsing, drying (e.g., hard baking), other suitableprocesses, and/or combinations thereof. The photolithography exposingprocess may also be implemented or replaced by other proper methods suchas maskless photolithography, electron-beam writing, and ion-beamwriting. The etching processes include dry etching, wet etching, and/orother etching methods (e.g., reactive ion etching). The etching processcan also be either purely chemical (wet etching), purely physical (ionmilling), and/or combinations thereof. It is understood that the gatestructures may be formed simultaneously, utilizing the same processingsteps and processing materials; independently of one another, utilizingvarying processing steps and processing materials; or using acombination of simultaneous and independent processing steps andprocessing materials.

In the present embodiment, gate stacks comprising the interfacial layer416, high-k dielectric layer 418, etch stop layer 420, capping layer422, and dummy gate layer 424 are formed by any suitable process,including the processes described herein. For example, a layer ofphotoresist is formed over the dummy gate layer by a suitable process,such as spin-on coating, and patterned to form a patterned photoresistfeature. The pattern of the photoresist can then be transferred by a dryetching process to the underlying layers (i.e., the interfacial layer416, high-k dielectric layer 418, etch stop layer 420, capping layer422, and dummy gate layer 424) to form the gate stacks as shown in FIG.4B. The photoresist layer may be stripped thereafter. In anotherexample, a hard mask layer is formed over the dummy gate layer; apatterned photoresist layer is formed on the hard mask layer; thepattern of the photoresist layer is transferred to the hard mask layerand then transferred to the dummy gate layer 424 and underlying layers(interfacial layer 416, high-k dielectric layer 418, etch stop layer420, and capping layer 422) to form the gate stack of the gatestructures. It is understood that the above examples do not limit theprocessing steps that may be utilized to form the gate stack. It isfurther understood that the gate stack of the gate structures maycomprise additional layers. For example, the gate structures maycomprise interfacial layers, capping layers, diffusion/barrier layers,conductive layers, other suitable layers, and/or combinations thereof.Also, the semiconductor device 400 may include one or moreantireflective coating layers (e.g., a top antireflective coating layerand/or a bottom antireflective coating layer).

Additional features are subsequently formed for the gate structures asillustrated in FIG. 4C. For example, spacers may further be formed onthe sidewalls of the gate stacks. In the present embodiment, spacerliner 426 and gate spacers 428 are formed. The spacer liner 426 and gatespacers 428 are formed by any suitable process to any suitablethickness. The spacer liner 426 may comprise an oxide material (e.g.,silicon oxide), and the gate spacers 428, which are positioned on eachside of the gate stacks, may comprise a nitride material (e.g., siliconnitride). In various examples, the gate spacers 428 may comprise adielectric material such as silicon nitride, silicon carbide, siliconoxynitride, other suitable materials, and/or combinations thereof. Thegate spacers 428 may be used to offset subsequently formed dopedregions, such as heavily doped source/drain regions. The gate structuresmay further include a sealing layer and any other suitable feature.

Various doped regions may also be formed in the substrate 410. In thepresent embodiment, various doped regions comprise lightly dopedsource/drain (LDD) regions 430, 431 and source/drain (S/D) regions 432,433 (also referred to as heavily doped S/D regions). The LDD regions430, 431 and S/D regions 432, 433 may be formed by one or more ionimplantation processes, photolithography, diffusion, and/or othersuitable processes. The doping species may depend on the type of devicebeing fabricated, such as an NMOS or PMOS device. For example, the LDDand S/D regions 430, 432 in the first/NMOS region 411A are doped withn-type dopants, such as phosphorus or arsenic; and the LDD and S/Dregions 431, 433 in the second/PMOS region 411B are doped with p-typedopants, such as boron or BF₂. The LDD regions 430, 431 and S/D regions432, 433 may comprise various doping profiles. It is understood that theLDD regions may be formed prior to formation of the gate spacers 428.Additionally, one or more annealing processes may be performed toactivate the LDD regions 430, 431 and/or S/D regions 432, 433. Theannealing processes comprise rapid thermal annealing (RTA) and/or laserannealing processes. The S/D regions 432, 433 may be aligned with anouter edge of the spacers 428 following the one or more implantationprocesses.

The doped regions may be formed directly in the semiconductor substrate,in a P-well structure, in a N-well structure, in a dual-well structure,or using a raised structure. The S/D regions 432, 433 may compriseraised S/D regions, which are formed by one or more epitaxy processes,such that SiGe features can be formed in a crystalline state in thesubstrate 410. For example, in the present embodiment, in the secondregion 411B, the S/D regions 433 further include raised S/D regions 434.The epitaxy processes include CVD deposition techniques (e.g.,vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD (UHV-CVD)),molecular beam epitaxy, and/or other suitable processes. The epitaxyprocess may use gaseous and/or liquid precursors, which interact withthe composition of the substrate 410 (e.g., silicon). Thus, a strainedchannel may be achieved in the first or second regions 411A, 411B,depending on device configuration, to increase carrier mobility andenhance device performance.

As noted above, the final thickness of the interfacial layer 416 dependson subsequent thermal budget processes. Typically, the high thermalbudget processes, such as the S/D annealing processes, cause re-growthof the interfacial layer 416, which leads to a thicker interfacial layer416 and increased EOT. In the present embodiment, during these processes(and the subsequent gate replacement processes that will be discussedfurther below), the low thermal budget silicon capping layer 422controls the oxygen content in the etch stop layer 420, and the etchstop layer 420 absorbs oxygen from the interfacial layer 416, whichultimately results in reducing the thickness of the interfacial layer416 and providing EOT scaling.

One or more contact features 436, 437, such as silicide regions, mayalso be formed. The contact features 436, 437 may be coupled to the S/Dregions 432, 433. The contact features 436, 437 comprise silicidematerials such as nickel silicide (NiSi), nickel-platinum silicide(NiPtSi), nickel-platinum-germanium silicide (NiPtGeSi),nickel-germanium silicide (NiGeSi), ytterbium silicide (YbSi), platinumsilicide (PtSi), iridium silicide (IrSi), erbium silicide (ErSi), cobaltsilicide (CoSi), other suitable conductive materials, and/orcombinations thereof. The contact features 436, 437 are formed by anysuitable process, including the processes described herein. For example,the contact features 436, 437 may be formed by a salicide (self-alignedsilicide) process. A metal material may be deposited over the substrate,including over the substrate (e.g., silicon regions) and/or dopedregions. After deposition, the salicidation process may continue with areaction between the deposited metal material and the silicon regions atan elevated temperature that is selected based on the specific metalmaterial or materials. This is also referred to as annealing, which maybe a RTP. The unreacted metal material is removed thereafter. Thereacted silicide may require additional thermal process to reduce theresistance of the silicide.

A dielectric layer 440 is disposed over the substrate 410, such as aninterlayer (or inter-level) dielectric (ILD) layer. The dielectric layer440 comprises any suitable dielectric material including TEOS oxide,silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide,zirconium oxide, titanium oxide, aluminum oxide, hafnium dioxide-alumina(HfO₂—Al₂O₃) alloy, PSG, BPSG, other suitable dielectric materials,and/or combinations thereof. Alternatively, the dielectric layer 440comprises a low-k dielectric material, such as fluorinated silica glass(FSG), carbon doped silicon oxide, Black Diamond® (Applied Materials ofSanta Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon,Parylene, BCB (bis-benzocyclobutenes), SiLK (Dow Chemical, Midland,Mich.), polyimide, other proper materials, and/or combinations thereof.The dielectric layer 440 may further include a multilayer structurecomprising multiple dielectric materials. The dielectric layer 440 isformed by any suitable process to any suitable thickness, including byCVD, high density plasma CVD, spin-on, sputtering, and/or other suitablemethods. After the dielectric layer 440 is deposited, one or morechemical mechanical polishing (CMP) processes can be performed. It isunderstood that additional layers may be formed overlying and/orunderlying the dielectric layer 440.

Referring to FIGS. 4D-4G, at block 314, a gate replacement process isperformed. More particularly, a metal gate may replace the dummy polygate of the gate structures (i.e., a gate layer replaces the dummy gatelayer 424). A first metal gate is formed in the first gate structure,and a second gate structure is formed in the second gate structure. Thefirst and second metal gates are formed by any suitable process. Forexample, as illustrated in FIGS. 4D and 4F, portions of the first gatestructure and the second gate structure are removed, thereby formingopenings (trenches) in the gate structures. For example, the dummy gatelayer 424 and capping layer 422 are removed from the gate structures byany suitable process. In an example, removing dummy gate layer 424 andcapping layer 422 includes one or more etching processes, including wetetching processes, dry etching processes, or combinations thereof.Another example includes forming a photoresist layer over thesemiconductor device 400; patterning the photoresist layer by aconventional photolithography process; and etching the dummy gate layer424 and capping layer 422 within the pattern of the photoresist layer.Subsequently, the photoresist layer may be removed. It is understoodthat the dummy gate layer 424 may be removed simultaneously with orindependent of the capping layer 422. It is further understood thatadditional portions of the gate structures can be removed, such as theetch stop layer 420 and/or high-k dielectric layer 418.

A first metal gate and second metal gate are formed in the openings(trenches), which were formed by removing portions of the gatestructures, for example, the dummy gate layer 424 and the capping layer422. Referring to FIGS. 4E and 4G, the first and second metal gatesinclude first and second gate layers 442, 443 and conductive layers 444,445. The first gate layer 442 may have a first work function, and thesecond gate layer 443 may have a second work function. The first andsecond metal gates may further comprise liner layers, work functionlayers, fill layers, other suitable layers, and/or combinations thereof.

The first and second gate layers 442, 443 are formed by any suitableprocess. The first and second gate layers 442, 443 partially fill in theopenings (trenches) of the gate structures. The first and second gatelayers 442, 443 comprise a work function layer. Thus, in the first/NMOSregion 411A, an exemplary first gate layer 442 includes a work functionlayer for an NMOS device, such as tantalum, titanium aluminum, titaniumaluminum nitride, or combination thereof; and in the second/PMOS region411B, an exemplary second gate layer 443 includes titanium nitride,tantalum nitride, or combinations thereof. Alternatively, the first andsecond gate layers 442, 443 include any suitable material, such asaluminum, copper, tungsten, titanium, tantulum, titanium nitride,tantalum nitride, nickel silicide, cobalt silicide, silver, TaC, TaSiN,TaCN, TiAl, TiAlN, WN, metal alloys, other suitable materials, and/orcombinations thereof.

The first and second conductive layers 444, 445 are formed over thefirst and second gate layers 442, 443 by any suitable process. The firstand second conductive layers 444, 445 substantially fill in theremainder of the openings (trenches) of the gate structures. The firstand second layers 444, 445 include any suitable material, such asaluminum, copper, tungsten, titanium, tantulum, titanium nitride,tantalum nitride, nickel silicide, cobalt silicide, silver, TaC, TaSiN,TaCN, TiAl, TiAlN, WN, metal alloys, other suitable materials, and/orcombinations thereof. In the present example, the first and secondconductive layers 444, 445 comprise aluminum. The aluminum is depositedby an ALD or PVD process. Alternatively, the first conductive layer 444comprises a material different than the second conductive layer 445.Subsequently, one or more CMP processes may be performed to planarizethe first and second conductive layers 444, 445.

The semiconductor device 400 may undergo further CMOS or MOS technologyprocessing to form various features known in the art. Subsequentprocessing may form various contacts/vias/lines and multilayerinterconnect features (e.g., metal layers and interlayer dielectrics) onthe substrate 410, configured to connect the various features orstructures of the semiconductor device 400. The additional features mayprovide electrical interconnection to the device including the formedmetal gate structures. For example, a multilayer interconnectionincludes vertical interconnects, such as conventional vias or contacts,and horizontal interconnects, such as metal lines. The variousinterconnection features may implement various conductive materialsincluding copper, tungsten, and/or silicide. In one example a damasceneand/or dual damascene process is used to form a copper relatedmultilayer interconnection structure.

In summary, a gate replacement process is provided. The gate replacementprocess described implements an etch stop layer and a capping layerincluding a low thermal budget silicon. The gate replacement process maybe implemented to form an integrated circuit device having one or moregate structures. The disclosed method may be easily integrated intoconventional integrated circuit processing, particularly in high-k/metalgate device fabrication, and can provide equivalent oxide thicknessreduction. In an example, the method comprises forming a material layerover a substrate; forming an etch stop layer over the material layer;forming a capping layer including low thermal budget silicon over theetch stop layer; forming a dummy gate over the capping layer; forming agate structure; and forming a first metal gate in the first gatestructure. Forming the first metal gate in the first gate structure mayinclude replacing the dummy gate with a metal gate having a workfunction layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for fabricating an integrated circuitdevice, the method comprising: providing a substrate; forming aninterfacial layer over the substrate; forming a high-k dielectric layerover the interfacial layer; forming an etch stop layer over the high-kdielectric layer; forming a capping layer including a low thermal budgetsilicon layer over the etch stop layer; forming a dummy gate layer overthe capping layer; forming a gate structure; and performing a gatereplacement process.
 2. The method of claim 1 further comprisingperforming a high thermal budget process to form one or more features onthe substrate.
 3. The method of claim 1 wherein performing the highthermal budget process comprises performing a source/drain annealingprocess.
 4. The method of claim 1 wherein forming an etch stop layerover the high-k dielectric layer comprises depositing a titanium nitridelayer.
 5. The method of claim 1 wherein forming the capping layercomprises performing a physical vapor deposition process to deposit alayer of silicon.
 6. The method of claim 1 wherein forming the dummygate layer comprises performing a low pressure chemical vapor depositionprocess to deposit a layer of silicon.
 7. The method of claim 1 whereinforming the gate structure comprises performing a patterning process toform a gate stack including the interfacial layer, high-k dielectriclayer, low thermal budget silicon layer, and dummy gate layer.
 8. Themethod of claim 7 wherein performing the patterning process to form thegate stack including the interfacial layer, high-k dielectric layer, lowthermal budget silicon layer, and dummy gate layer comprises: forming afirst gate stack and a second gate stack; replacing at least the lowthermal budget silicon layer and dummy gate layer in the first gatestack with a first metal gate; and replacing at least the low thermalbudget silicon layer and dummy gate layer in the second gate stack witha second metal gate.
 9. The method of claim 1 wherein performing thegate replacement process comprises replacing the low thermal budgetsilicon layer and dummy gate layer with a metal gate.
 10. The method ofclaim 9 wherein replacing the low thermal budget silicon layer and dummygate layer with the metal gate comprises: forming a metal gate for anNMOS device; and forming a metal gate configured for a PMOS device. 11.A method for fabricating an integrated circuit device, the methodcomprising: forming a material layer on a substrate; forming an etchstop layer on the material layer; forming a capping layer that includessilicon on the etch stop layer; forming a dummy gate layer on thecapping layer; patterning the material layer, the etch stop layer, thecapping layer, and the dummy gate layer to form a gate stack; removingthe patterned dummy gate layer and the patterned capping layer from thegate stack; and forming a conductive layer over the patterned etch stoplayer.
 12. The method of claim 11, wherein the material layer includesan interfacial layer and a high-k dielectric layer over the interfaciallayer.
 13. The method of claim 11, wherein forming the conductive layerover the etch stop layer occurs after removing the patterned dummy gatelayer and the patterned capping layer from the gate stack.
 14. Themethod of claim 11, wherein the etch stop layer includes one oftitanium, titanium nitride, tantalum, and tantalum nitride.
 15. Themethod of claim 11, wherein forming the conductive layer over thepatterned etch stop layer includes forming the conducting layer directlyon the patterned etch stop layer.
 16. A method for fabricating anintegrated circuit device, the method comprising: forming a materiallayer on a substrate; forming an etch stop layer on the material layer;forming a capping layer that includes silicon on the etch stop layer;forming a dummy gate layer on the capping layer; patterning the materiallayer, the etch stop layer, the capping layer, and the dummy gate layerto form a first gate stack and a second gate stack; removing thepatterned dummy gate layer and the patterned capping layer from thefirst and second gate stacks; and forming a first conductive layerhaving a first work function over the patterned etch stop layer in thefirst gate stack and forming a second conductive layer having a secondwork function over the patterned etch stop layer in the second gatestack, the first work function being different than the second workfunction.
 17. The method of claim 16, wherein removing the patterneddummy gate layer and the patterned capping layer from the second gatestack occurs after forming the first conductive layer having the firstwork function over the patterned etch stop layer in the first gatestack.
 18. The method of claim 16, wherein the etch stop layer includestitanium nitride.
 19. The method of claim 16, wherein the material layerincludes an interfacial layer and a high-k dielectric layer.
 20. Themethod of claim 16, performing a thermal budget process to form one ormore features on the substrate after patterning the material layer, theetch stop layer, the capping layer, and the dummy gate layer to form thefirst gate stack and the second gate stack.